Sym plasmid of Rhizobium trifolii expressed in different rhizobial species and Agrobacterium tumefaciens

Hooykaas, Paul J. J.; Brussel, A. A. N. Van; Dulk-Ras, H. den; Slogteren, G. M. S. van; Schilperoort, R. A.

doi:10.1038/291351a0

Cited by 265 publications

(128 citation statements)

References 16 publications

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“…The uniformity of this background has been supported by different types of data; the symbionts of peas, clovers, and beans cannot reliably be distinguished on the basis of phenotypic characteristics (17). Under laboratory conditions, recombination of chromosomal genes among isolates belonging to the different biovars can be obtained easily (9,13); symbiotic plasmids conferring different symbiotic capacities can be transferred among strains isolated from peas, clovers, and beans and remain functional (7,10,14). DNA-DNA hybridization levels are higher among isolates belonging to the three biovars than to isolates belonging to other related species (3); the nucleotide sequences of a 16s rDNA fragment from different isolates obtained from peas, clovers, and beans have been found to be identical (6,25).…”

mentioning

confidence: 94%

Reclassification of American Rhizobium leguminosarum Biovar Phaseoli Type I Strains as Rhizobium etli sp. nov.

Segovia¹,

Young

Martı́nez-Romero³

1993

International Journal of Systematic Bacteriology

377

190

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A new Rhizobium species that nodulates Phaseolus vulgaris L. is proposed on the basis of a sequence analysis of 16s ribosomal DNA. This taxon, Rhizobium etli sp. nov., was previously named Rhizobium leguminosarum biovar phaseoli (type I strains) and is characterized by the capacity to establish an effective symbiosis with bean plants, the reiteration of the nitrogenase structural genes, the organization of the common nodulation genes into two separate transcriptional units bearing nod4 and nodBC, the presence of the polysaccharide inhibition gene, psi, and the 16s ribosomal DNA sequence. An analysis of the sequence of a fragment of the 16s rRNA gene shows that this gene is quite different from the gene of R. leguminosarum. In addition, all R. etli strains have identical sequences. We describe these analyses and discuss additional evidence supporting our proposal.

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mentioning

confidence: 94%

Reclassification of American Rhizobium leguminosarum Biovar Phaseoli Type I Strains as Rhizobium etli sp. nov.

Segovia¹,

Young

Martı́nez-Romero³

1993

International Journal of Systematic Bacteriology

377

190

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“…In contrast to Rhizobium spp., Bradyrhizobium species are slow-growing (8), nitrogen-fixation and nodulation genes are located on the chromosome (9) and not on plasmids (10)(11)(12), and less is known about the genetic requirements for nodulation (13)(14)(15). In particular, the compounds produced by the soybean host that interact with the common nod genes have not been characterized.…”

mentioning

confidence: 99%

Induction of Bradyrhizobium japonicum common nod genes by isoflavones isolated from Glycine max

Kosslak¹,

Bookland²,

Barkei³

et al. 1987

Proc. Natl. Acad. Sci. U.S.A.

376

225

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The early events in legume nodulation by Rhizobium spp. involve a conserved gene cluster known as the common nod region. A broad-host-range plasmid (pEA2-21) containing a Bradyrhizobium japonicum nodDABC-acZ translational fusion was constructed and used to monitor nod gene expression in response to soybean root extract. Two inducing compounds were isolated and identified. Analysis using ultraviolet absorption spectra, proton nuclear magnetic resonance, and mass spectrometry showed that the two inducers were 4',7-dihydroxyisoflavone (daidzein) and 4',5,7-trihydroxyisoflavone (genistein). Induction was also seen with some, but not all, of the flavonoid compounds that induce nod genes in fast-growing Rhizobium strains that nodulate clover, alfalfa, or peas. When pEA2-21 was introduced into Rhizobium trifohii, it was inducible by flavones but not by daidzein and genistein. In Rhizobium fredii, pEA2-21 was induced by isoflavones and flavones. Thus, the specificity of induction appears to be influenced by the host-strain genome.Members of the bacterial genus Rhizobium form symbiotic associations with leguminous plants that result in the formation of nitrogen-fixing root nodules. In three agronomically important Rhizobium/legume associations, R. trifolii/clover, R. meliloti/alfalfa, and R. leguminosarum/pea, important bacterial nodulation genes (1-4) and plant compounds that induce them (5-7) have been identified. In these associations flavones (5-7) or flavanones (7) have been found to induce the nodABC genes, as well as other nod genes involved in host specificity (1). Isoflavones have been found to inhibit the induction of nodABC in R. leguminosarum (7).The Bradyrhizobium japonicum/soybean symbiosis is of considerable agricultural importance. In contrast to Rhizobium spp., Bradyrhizobium species are slow-growing (8), nitrogen-fixation and nodulation genes are located on the chromosome (9) and not on plasmids (10)(11)(12), and less is known about the genetic requirements for nodulation (13)(14)(15). In particular, the compounds produced by the soybean host that interact with the common nod genes have not been characterized.In this study, a nodABC-lacZ translational fusion was used to monitor nod gene expression in B. japonicum in response to soybean root extract. Two major components from soybeans (Glycine max cv. Williams) were isolated that induced the expression of the nodABC-lacZ fusion when it was present in the soybean-nodulating bacteria B. japonicum and Rhizobium fredii, but not when it was present in R. trifolii. MATERIALS AND METHODSStrains and Plasmids. Standard procedures (16) were used for DNA manipulations. A HindIII fragment containing the nod region of B. japonicum USDA 123 was cloned in both orientations into the single HindIII site of plC19R (17). BamHI-Bgl II fragments containing the nod genes and flanking polylinker sequences were then cloned into the BamHI site of the broad-host-range vector pGD926 (18) resulting in pEA2-21 and pEA4-10 (Fig. 1) (19) agar and germinated for 3 days in the d...

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“…We cannot easily explain this exception at present. One might conjecture that @genes being located on large indigenous plasmids [ 13-151 can be transferred by conjugation [16] from one Rhizobium strain to another and that strain RCR 3211 has acquired nif genes from a fast-growing strain in this way. These results confirm that rhizobia of the fast and slowgrowing groups are taxonomically not closely related.…”

Section: Discussionmentioning

confidence: 99%

An immunological comparison of nitrogenase proteins of fast and slow growing rhizobia

et al. 1982

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Sym plasmid of Rhizobium trifolii expressed in different rhizobial species and Agrobacterium tumefaciens

Cited by 265 publications

References 16 publications

Reclassification of American Rhizobium leguminosarum Biovar Phaseoli Type I Strains as Rhizobium etli sp. nov.

Reclassification of American Rhizobium leguminosarum Biovar Phaseoli Type I Strains as Rhizobium etli sp. nov.

Induction of Bradyrhizobium japonicum common nod genes by isoflavones isolated from Glycine max

An immunological comparison of nitrogenase proteins of fast and slow growing rhizobia

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